docs: update README to clarify QQ group label

- Changed the label for the QQ group in the README from "QQ群" to "QQ 群" for consistency and clarity.

Author: oboard

README.md

@@ -149,4 +149,4 @@ fn main {
 
 QQ 群号：**949886784**
 
-![QQ群](qrcode.jpg)
+![QQ 群](qrcode.jpg)